An FTN number is informal shorthand for a federal Taxpayer Identification Number, which the IRS officially calls a TIN. It’s the nine-digit number the IRS uses to track your tax activity, and every person or business that files a federal return needs one. You won’t find “FTN” in IRS publications or on IRS.gov; the agency uses “TIN” across all its forms and correspondence. Banks, foreign governments, and some financial paperwork use “FTN” or “Federal Tax Number” loosely, but they’re pointing at the same thing.1Internal Revenue Service. Taxpayer Identification Numbers (TIN)
Which number you actually need depends on who you are and what you’re doing. The Social Security Administration issues one type; the IRS issues the rest.
The Five Kinds of TINs
The IRS recognizes five taxpayer identification numbers. Most people only ever deal with one or two of them.
Social Security Number
The SSN is the most common TIN. The Social Security Administration issues it to U.S. citizens and to noncitizens authorized to work here. You need one to start a job, file taxes, open a bank account, apply for a loan, or claim government benefits.2Social Security Administration. Request a Social Security Number for the First Time The SSA also issues cards to some noncitizens with a valid nonwork reason, such as qualifying for a federally funded benefit.3Social Security Administration. Your Social Security Number and Card
Individual Taxpayer Identification Number
An ITIN is a nine-digit number the IRS issues to people who have to file a federal tax return but can’t get an SSN. That typically covers nonresident aliens with U.S. tax obligations, resident aliens who aren’t SSN-eligible, and their spouses or dependents.4Internal Revenue Service. Individual Taxpayer Identification Number (ITIN)
An ITIN exists only for federal tax purposes. It does not authorize you to work in the United States, change your immigration status, qualify you for Social Security benefits, or make you eligible for the Earned Income Tax Credit.4Internal Revenue Service. Individual Taxpayer Identification Number (ITIN) Some banks accept an ITIN to open an account, but policies vary.
Employer Identification Number
An EIN is the nine-digit number the IRS assigns to business entities. Corporations, partnerships, estates, trusts, and nonprofits all need one.5Internal Revenue Service. About Form SS-4, Application for Employer Identification Number Sole proprietors can often use their SSN for business taxes, but an EIN becomes mandatory once you hire employees, operate as a partnership or corporation, pay excise taxes, change your business structure, or administer a retirement plan, trust, or estate.6Internal Revenue Service. Get an Employer Identification Number Plenty of sole proprietors get one anyway, just to keep their SSN off invoices and vendor forms.
Adoption and Preparer TINs
Two others cover narrow situations. An Adoption Taxpayer Identification Number (ATIN) is a temporary number for a child being adopted when the adoptive parents can’t yet obtain the child’s SSN.7Internal Revenue Service. Adoption Taxpayer Identification Number A Preparer Tax Identification Number (PTIN) is required for anyone who prepares federal tax returns for compensation.8Internal Revenue Service. IRS Reminds Tax Pros to Renew PTINs for the 2026 Tax Season
When You Need One
Every federal tax return requires a TIN. Without one, the IRS can’t process your return, and you can’t receive a refund. Tax filing is only the beginning. Employers need your TIN to withhold and report wages. Banks need it to open most accounts. Clients need it to pay you for freelance or contract work.
Businesses have their own triggers. Third-party payment platforms like Venmo or PayPal must file Form 1099-K when a payee’s gross payments exceed $20,000 and the number of transactions exceeds 200 in a calendar year, and they need your TIN to do it.9Internal Revenue Service. IRS Issues FAQs on Form 1099-K Threshold Under the One, Big, Beautiful Bill; Dollar Limit Reverts to $20,000 If you don’t give a correct TIN to someone paying you, 24% backup withholding kicks in. The payer sends a quarter of what they owe you to the IRS, and you have to file to get it back.10Internal Revenue Service. Topic No. 307, Backup Withholding
How to Get the One You Need
SSN
To get your first Social Security Number, complete Form SS-5 and provide at least two documents proving your age, identity, and citizenship or immigration status. You can usually mail the signed application with original documents, which are returned to you, or bring everything in person. If you’re 12 or older and have never had an SSN, you must apply in person.11Social Security Administration. Application for a Social Security Card
ITIN
File Form W-7 with documents proving both foreign status and identity.12Internal Revenue Service. Form W-7 – Application for IRS Individual Taxpayer Identification Number You have three submission routes:
- By mail, with your tax return and original or certified identification documents.
- In person at an IRS Taxpayer Assistance Center.
- Through an IRS-authorized Acceptance Agent, who reviews your documents and submits on your behalf so you don’t mail originals.
Processing runs about seven weeks. During tax season (January 15 through April 30) or if you apply from overseas, expect 9 to 11 weeks.4Internal Revenue Service. Individual Taxpayer Identification Number (ITIN)
EIN
Businesses apply using Form SS-4. The IRS online application is free and issues the EIN immediately upon approval, and it’s open to applicants with a legal residence or principal business location in the United States or U.S. territories.13Internal Revenue Service. Instructions for Form SS-4 – Application for Employer Identification Number If you can’t use the online tool, fax applications are typically processed in about four business days, and mailed applications take roughly four weeks.6Internal Revenue Service. Get an Employer Identification Number
If Your ITIN Expires
ITINs don’t last forever. If you don’t use yours on a federal tax return for three consecutive years, it automatically expires on December 31 after that third year of non-use.14Internal Revenue Service. How to Renew an ITIN Filing with an expired ITIN delays your refund until you complete renewal.
To renew, submit a new Form W-7 with the same supporting documents required for the original application. You can renew by mail, in person at a Taxpayer Assistance Center, or through an Acceptance Agent. The IRS recommends renewing before you file so processing isn’t held up.
What It Costs to Skip It
For individuals, the IRS charges $50 for each missing TIN required on a return or statement, up to $100,000 per calendar year.15Internal Revenue Service. Information About Your Notice, Penalty and Interest
Businesses face separate penalties for information returns like 1099s filed with missing or incorrect TINs. The amount depends on how quickly you fix it:
- Corrected within 30 days: $60 per return.
- Corrected by August 1: $130 per return.
- Not corrected after August 1: $340 per return.
- Intentional disregard: $680 per return, with no cap.
These apply separately to the failure to file a correct information return and the failure to provide a correct payee statement, so the real cost can double.16Internal Revenue Service. Information Return Penalties The IRS may reduce or remove penalties for reasonable cause, but not knowing you needed a TIN rarely qualifies.
Then there’s the 24% backup withholding, which hits any payment where the payee hasn’t furnished a correct TIN. The money goes to the IRS, and you only recover it by filing a return and claiming a refund.10Internal Revenue Service. Topic No. 307, Backup Withholding If you’re a freelancer or gig worker, losing a quarter of every check until the paperwork is sorted out is a serious cash-flow problem.